2.0 Analysis 2.1 Management and Supervision On 30 April 1999, at about 1800, the departure controller was involved in an operating irregularity in which there was a loss of separation. The on-duty shift manager assessed the controller as being capable of returning to work on his next scheduled shift. However, there was no assessment of the controller the following morning by the on-duty shift manager or the team supervisor. It could not be determined if such an assessment would have influenced the decision to have the controller return to duty; however, had such an assessment been required, the team supervisor would have been aware that one of the duty controllers had had an operating irregularity. The team supervisor would then have had the option, as provided for in the statement of duties, of conducting a proficiency check through stand-back supervision during the controller's initial period of return to duty. 2.2 The Nine/Ten Split vs. Look and Go The nine/ten split is a procedure that was established and has been in use for about 17 years in the Calgary TCU. It provides for positive vertical separation when aircraft are in proximity to the airport and manoeuvring to the landing runway or when aircraft are receiving their initial headings to establish themselves on their outbound tracks. When used, this procedure reduces the controller's workload because the need for close monitoring of the traffic is less than that required by the look and go method. 2.3 Traffic Separation Aircraft separation from other known IFR or VFR traffic is the responsibility of the controller responsible for that aircraft. In the situation of the arriving ACA270 and departing CDN960, the arrival controller and departure controller shared that responsibility; however, the departure controller has the responsibility of keeping his traffic clear of inbound landing traffic. It is therefore important that the controllers communicate. Communication becomes imperative if one individual is uncertain of the intentions of the other. In the situation that arose with ACA270 and CDN960, the arrival controller recognized early that the two aircraft might be placed in proximity to each other. He took the initiative by communicating to the departure controller that ACA270 was still at 10 000 feet. When the departure controller did not respond with a verbal acknowledgement, change the altitude clearance limit for CDN960, or cancel the code for ACA270, the arrival controller did not take any further action to ensure that the departure controller was aware of his concerns. Nor did he take positive action at that time to ensure separation between the aircraft he was controlling and CDN960. 2.4 Departure Controller It could not be determined how the prior day's occurrence influenced the departure controller on the morning of 01 May 1999. The departure controller's schedule for April 1999 showed several changes from the controlled shift schedule. These changes were the result of both his and management's requests. Of the 30 shift possibilities, only five (17 per cent) were unchanged. Scheduled days off were largely exchanged for overtime and, of the eight days off, five were due to the controller taking vacation. Shift work has the potential to impair an individual's ability to function at peak efficiency. The beneficial effects of controlled shift work, in maintaining an individual's efficiency, however, have been well documented by the scientific community. 3.0 Conclusions 3.1 Findings as to Causes and Contributing Factors The departure controller cleared the departing aircraft to an altitude above 9 000 feet prior to establishing that there would be adequate separation from arriving aircraft. The departure controller attached a code to the radar data block of the arriving aircraft, removing the restriction for that aircraft to maintain a minimum of 10 000 feet prior to reaching the dump point. The arrival controller recognized that there was a possibility of a conflict between ACA270 and CDN960, but he did not communicate that concern in a manner that was understood by the departure controller, nor did he take positive actions of his own to prevent the loss of separation. The departure controller had the option of using a nine/ten split for aircraft separation but chose to employ a look and go option that required close monitoring of the inbound and outbound traffic. 3.2 Other Findings The Calgary TCU specialty staffing was appropriate for the traffic complexity. The departure controller's workload was assessed as low with low complexity. The Calgary TCU specialty team supervisor was preparing the data position at the time of the occurrence. The departure controller was involved in a loss of separation the previous day. The Calgary TCU specialty team supervisor was not aware that the departure controller had been involved in an operating irregularity during the previous day. The on-duty shift manager did not meet with the departure controller prior to his resumption of duties on 01 May 1999. In the 30 days prior to the occurrence, the departure controller had worked an irregular shift schedule that had been changed several times at his or management's request. 4.0 Safety Action 4.1 Edmonton ACC Management 4.1.1 Information Documentation The management of the Edmonton ACC has instituted a temporary procedure whereby the shift managers provide written documentation to their relief in the form of electronic mail on issues that have arisen during their shift. These electronic messages are accessed by the oncoming shift manager at the beginning of each shift and continue to be supplemented by verbal shift-change briefings. The electronic messages are available to all managers and are maintained so that an historical record is available. The Manager, Area Control Centre Operations is developing a formal shift-manager information database that will replace the electronic mail system. 4.1.2 Operating Irregularities A procedure has been instituted at the Edmonton ACC for handling operating irregularities. The shift manager responsible for removing a controller from duty is now responsible for ensuring that all the appropriate steps are taken to reinstate a controller to duty. This includes the requirement for the controller involved in an operating irregularity to be interviewed by the duty shift manager immediately prior to being returned for duty. The ACC has also instituted a policy whereby all controllers involved in an operating irregularity are required to undergo a proficiency check before being reinstated to duty. 4.2 NAV CANADA NAV CANADA's National Mandatory Air Traffic Control Refresher Training Plan for 1999/2000 and 2000/2001 notes that the Technical Training Division of NAV CANADA is committed to the development and complete delivery by 31 August 2001 of two 1-day human factors training modules on communications and on teamwork. The aim of the communications module is to make participants aware of the danger of poor or confusing communication in the operational environment. The aim of the teamwork module is to make participants aware of how an individual's skill and performance affect collaborative work and decision making. 4.3 Transport Canada Transport Canada is chairing a tripartite working group on controller fatigue. Included in the working group are representatives from NAV CANADA, the Canadian Air Traffic Control Association, and Transport Canada. The related steering committee is chaired by the Assistant Deputy Minister, Safety and Security.